1. Field of the Invention
This invention relates to weapon systems, and more specifically to weapon systems which track maneuvering targets and launch terminally guided projectiles toward targets.
2. Description of the Prior Art
One type of weapon system which is intended to destroy enemy ground-based or airborne targets uses as weapons unguided projectiles or missiles against targets with relatively low target acceleration capability. Other systems have been developed which require a means for tracking the target, a means for tracking a projectile or missile initially aimed at the target, and a means for reducing or eliminating the miss vector between the target and the projectile or missile. The means for reducing or eliminating the miss vector provides guidance to the projectile or missile so that the projectile or missile will proceed to either hit the target directly or explode in such close vicinity to the target lethal zone so as to fatally damage the target. Most anti-airborne and anti-ground based target weapon systems provide continuous projectile or missile trajectory correction whereby information is sent to the projectile or missile at some predesignated data rate, so as to alter the course of the projectile or missile, and energy resources of the projectile are used throughout the course of the flight of the projectile or missile, or for some relatively lengthy terminal phase of the flight of the projectile, to maneuver the projectile or missile to within the lethal zone at the end of the flight of the projectile or missile. Furthermore, when a missile is used, guidance and control systems on board the missile are often actively employed in obtaining information about the target and/or computing corrections to its own flight path. Such guidance and control systems on board the missile greatly increase the cost of designing, manufacturing, testing, and maintaining the missile. Although the weapon guidance technique hereinbefore described has been demonstrated to be effective against relatively slowly accelerating targets, serious difficulties have arisen in attempting to eliminate targets which can rapidly accelerate as the weapon enters its terminal phase of the trajectory. When the weapon has been directed throughout its entire flight to the predicted location of the target, and uses most of its energy resources therefor, a rapid maneuver by a target, wherein the target severely deviates from its expected flight path, near the end of the flight of the weapon, cannot generally be compensated, since system delay times prevent the system from responding to rapid changes and sufficient energy resources to maneuver the weapon are no longer available to correct for extreme changes in the miss vector during the terminal phase of the flight of the weapon.
Modern weapon systems having purposes similar to the invention herein disclosed have been investigated and designed in the past two decades. A gun-fired missile system concept commonly referred to as POLCAT, was investigated by the Bulova Research and Development Laboratories. The POLCAT concept of weapon delivery employs a gun-launched anti-tank weapon with terminal trajectory correction using a semiactive guidance technique and impulse control. The POLCAT weapon system concept employs a frame-fixed target seeker for guidance and a single-impulse applied at the center of gravity normal to the longitudinal axis of the weapon for trajectory correction. The system operates by firing a missile, in a manner similar to that of a conventional gun system, when a target is engaged. In one version of POLCAT, an illuminator in the missile transmits pulsed radiation with a narrow radiation beam throughout the flight, which is required because ground targets, in general, do not have sufficiently intense or discrete signature. Correction of the missile trajectory is initiated when a line-of-sight control angle is determined which indicates an increasing miss of the target. By this technique, near misses are controlled close to the target and larger deviations are controlled further from the target, because a threshold angle for trajectory control is a constant value. The missile incorporates a forward-looking receiver that determines the pertinent angles to the target, so as to provide data to alter the trajectory of the missile.
The DRAGON missile system is a light-weight system designed to be carried by a foot soldier and fired against tanks or other targets within an approximate range of 1,000 meters, and intended for use as a medium anti-tank missile at the infantry platoon level. The system consists of a cylindrical missile, a portable launcher for firing the missile, a sighting means or "tracker" for visually following the missile in flight after launch, and appropriate electronic means for correcting the flight path of the missile during the flight from the launcher to the target. The missile is fired from a tubular launcher after the launcher is aimed at the designated target. The missile is required to be of a proper aerodynamic configuration and must rotate about its longitudinal axis in flight to maintain flight stability. The rotation, as well as aerodynamic stability of the missile, is provided by fins located in the aft area of the periphery of the missile. Guidance of the missile during flight is provided in the following manner. When the missile is launched, the soldier who fired the weapon sights the missile through an optical viewer throughout its flight to the target. The course of the missile is automatically corrected in flight by keeping the view of the missile as near as possible to the cross hairs of the optical viewer through which the soldier sights the missile and computing the deviation of the missile from its course to the target. The system is designed to keep the missile on a direct line-of-sight to the target, rather than having a fixed trajectory from the point of launch to a correction point near the target. The missile is kept on course by discharging (by explosion or detonation) small "thrusters" or jets which are built into the periphery of the missile from front to rear and discharged at an angle to the longitudinal axis of the missile. The timing and direction of application of the thrusters determine the direction of motion of the missile throughout the flight of the missile. The thrusters are fired electronically in the following manner. A light source is mounted in the tail of the missile. The beam of light from the light source impinges on an optical detector in the tracker component which senses whether the missile is above, below, to the right, or to the left of the line-of-sight from the tracker to the target. Depending upon the quadrant of the detector upon which the beam impinges, a signal is sent over a wire to the missile to fire one or more of the thrusters at a designated time and in a designated sequence so as to correct for deviations of the missile from the line-of-sight. The wire over which the signal is transmitted is wound on a spool, which is mounted on the rear of the missile, and the wire feeds out as the missile moves toward the target and maintains the connection between the tracker and the missile throughout the flight of the missile. The cost goal of the weapon round is $2,000-$2,500 and for the tracker of the missile is $8,000-$10,000, according to Aviation Week & Space Technology, "Program Slip Delays Export of Dragons," Feb. 3, 1975.